The present invention relates to the field of cable anchorages, such as may be used, for example, for anchoring longitudinal structural elements which are designed to be tensioned, such as wires, ropes, strands, tendons, stays or cables. In particular, but not exclusively, the invention relates to individual sealing arrangements for individual cable strands in such anchorages.
In order to illustrate the advantages of the invention, reference will be made to the application to stay cables. However, it should be understood that this application is not limiting, and that the principles underlying the invention may be applied to any kind of longitudinal structural elements which are designed to be tensioned, such as wires, ropes, strands, tendons, stays, cables etc.
Stay cables are used for supporting bridge decks, for example, and may typically be held in tension between an upper anchorage, secured to a tower of the bridge, and a lower anchorage, secured to the bridge deck. A stay cable may comprise dozens or scores of strands, with each strand comprising multiple (e.g. 7) steel wires. Each strand is usually retained individually in each anchorage, which may immobilise the strand using a tapered conical wedge seated in a conical hole in an anchor block, for example. Tensioning of the strands may be performed, from either one of the cable ends, using hydraulic jacks. The condition of the individual strands is typically monitored regularly to detect any corrosion or mechanical deterioration. If such deterioration is found in a particular strand, it may be de-tensioned, removed from the cable, replaced with a new strand and the new strand tensioned. If such a replacement operation is performed, great care must be taken to ensure that the new strand is sealed against ingress of moisture.
It has been proposed in European patent EP1227200B1, assigned to the same applicant, to provide individual sealing arrangements for each strand, so that an individual strand can be replaced and re-sealed without affecting the seals of the other strands. The proposed anchorage uses individual sealing rings, each held in place between two tight-fitting tubular elements which are assembled off-site, with the sealing ring trapped between them, when the anchorage is manufactured. When replacing a strand through this anchorage, care must be taken, when removing the old strand and inserting the new strand, not to damage the integrity of the seal. After tensioning, the exposed end of the cable may be protected by injecting grease or wax or gel into the cavity surrounding the strand inside the anchorage. The two tight-fitting tubular elements must be arranged such that, when replacing a strand, the two tubular parts do not move or deform relative to each other, and thereby permit a leak which may allow an ingress of moisture to circumvent the captive sealing ring. In such prior art the strand cannot be replaced easily without damaging the annular seal element 7 shown in FIG. 1 of EP1227200.